10min:

ANDREW R. CONRAD AND MICHAEL J. TUBERGEN, Department of Chemistry, Kent State University, Kent, Ohio 44242; RICHARD J. LAVRICH, Department of Chemistry and Biochemistry, College of Charleston, 66 George Street, Charleston, South Carolina 29424 .

The rotational spectra of the parent species of two conformers of the amino acid derivative leucinamide have been recorded between 10.5 and 20 GHz using a Balle-Flygare Fourier-transform microwave spectrometer. 6 a - and b -type rotational transitions were recorded for conformer I and 23 a - and b -type rotational transitions were recorded for conformer II. The rotational constants are A=2274.94(9) MHz, B=1033.336(7) MHz, and C=911.732(3) MHz and A=2752.775(8) MHz, B=843.502(1) MHz, and C=796.721(1) MHz for conformers I and II respectively. The congested hyperfine patterns arising from the two ¹⁴N nuclei were not resolved. Comparison of the experimental moments of inertia to those derived from the lowest energy ab initio (MP2/6-311++G(d,p)) structures indicates gas-phase backbone structures that differ from both the crystal structures of leucinamide and the gas-phase structures of the amino acid leucine\footnoteE. J. Cocinero, A. Lesarri, J.-U. Grabow, J. C. López, and J. L. Alonso, ChemPhysChem , 8 , 2007, 599-604..